Intercomparison 9711. pH, conductivity, alkalinity, nitrate + nitrite, chloride, sulfate, calcium, magnesium, sodium, potassium, total aluminium, reactive and non-labile aluminium, dissolved organic carbon, and chemical oxygen demand (ICP Waters report)
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- NIVA-rapport 
47 laboratories in 22 countries participated in intercomparison 9711. One sample set for the determination of major ions, organic matter and aluminium fractions, were used. Based on the general target accuracy of + 20%, 78% of the results were acceptable. More than 80% of the result pairs were acceptable for chloride, sulfate, calcium, mangnesium, sodium, dissolved organic carbon and chemical oxygen demand. For pH only 43% of the result pairs were acceptable in relation to the extended target accuracy of + 0.2 units. For three analytical variables, nitrate + nitrite, reactive and non-labile aluminium, it was decided not to evaluate the reported results, because of the extreme spread between the results from the partcipants. Normalization of the methods is necessary to improve the comparability for these variables. Manual methods are generally less sesitive compared to instrumental methods, and are not always suitable for acid rain monitoring.
PublisherNorsk institutt for vannforskning
ICP Waters report